McKinlay was the leading Democrat to replace Murphy, above, in Florida's 18th District race. (Tom Williams/CQ Roll Call File Photo)

Melissa McKinlay, the Democrat who was viewed as the party's front-runner in the highly contested race to replace Rep. Patrick Murphy, said Monday she will end her six-month-old campaign.

In an email to supporters , McKinlay said the entrance of millionaire businessman Randy Perkins into the race would make the cost for her to win "immense" and further distract from her day job as a Palm Beach County commissioner. "That revelation is a game changer for me and is not a compromise I will make for my constituents," she said. "A public servant’s integrity and trust are the assets citizens care about most. I will always make decisions to retain my integrity and remain worthy of your trust."

Democrats think that Trump at the top of the ticket will make their path to control of the Senate easier. (Spencer Platt/Getty Images)

Among those watching the White House race most closely a year from Election Day are those who stand to gain the most from the top-of-the-ticket contest. House and Senate candidates from both parties know their fates are closely tied to the fortunes of their parties’ respective presidential nominees and the tenor of the national conversation next November.

“Obviously the national environment is something that, to a certain extent, we have very little control over,” NRSC Communications Director Andrea Bozek said. “So our mentality is to prepare for the worst-case scenario.”

A Senate recruitment victory for Democrats in Florida could, in turn, jeopardize the party's quest for the House majority. Rep. Patrick Murphy, a favorite of national Democrats for the state's potentially open-seat Senate race, is announcing his statewide campaign Monday . That opens up the Treasure Coast-based House seat Murphy held for the past two cycles — one of just five Democrat-controlled House districts Mitt Romney carried in 2012.

Republicans have a voter registration advantage in the district, which Romney won by 4 points. It's a seat Republicans say they never should have lost in the first place, and they are even more optimistic with it open.

Rep. Patrick Murphy will run for Senate in the Sunshine State in 2016, giving national Democrats the candidate they want in a top pickup opportunity for the party this cycle.

“I’ve spent the last several months considering the best way I can continue to serve the people of Florida, and today, after much thought and discussion with people from across this state, I’m proud to announce that I will be a candidate for the United States Senate in 2016," Murphy said in a release announcing his bid Monday morning.

The Democratic Congressional Campaign Committee will announce Thursday the first 14 members who will join its Frontline program for the party's most vulnerable incumbents, according to an early copy of a news release obtained by CQ Roll Call.

The incumbents represent competitive districts, making them likely GOP targets in 2016 . The Frontline program,which Rep. Dan Kildee, D-Mich., is chairman of, provides these members with fundraising and organizational support for their re-elections.

Sinema is running for re-election in a competitive district in Arizona. (Bill Clark/CQ Roll Call File Photo)

All's fair in love and ... House races? Not so much.

Less than three weeks before Election Day, would-be safe incumbents such as Reps. Lee Terry, R-Neb., and Brad Schneider, D-Ill., are scrambling to win in partisan districts — while these 10 members are headed for victory in otherwise competitive districts.

Miami Dade School Board Member Carlos Curbelo won the Republican nomination and will face Democratic Rep. Joe Garcia in the fall in Florida's 26th District, Curbelo had 48 percent of the vote when the AP called the primary for him.

Republicans smell blood with Garcia, both because the district is competitive and because of ethical problems within his staff . Still, quarter after quarter, Garcia has put away massive financial hauls for the fall campaign ahead. As of his most recent campaign financial report, the freshman was closing in on $2 million in the bank. The race is rated Tilts Democrat by the Rothenberg Political Report/Roll Call.

Rep. Patrick Murphy's campaign made its first ad buy Monday in Florida's 18th District, reserving $1.4 million in cable and broadcast in the West Palm Beach-Treasure Coast media market, according to figures shared first with CQ Roll Call.

The Democrat's buy runs through the summer and into the fall in this district, located in the northeast corner of Palm Beach County, according to his campaign.